Losing connection to external USB harddisk (El Capitan)

[booterror1973]

I can not make anymore Time Machine backups on my external USB harddisk.
It's looking like the MacBookPro is losing connection to the harddisk, warning that i have to deattach de harddisk manual.

Does anybody know a solution?

 

[Just_Me_D]

I don't. Having said that, is there a time out/sleep option that may be enabled that's causing the disconnect?

 

[booterror1973]

I never changed settings.